Automatic optical inspection system &amp; method

ABSTRACT

A system comprising automatic apparatus for automatic optical inspection (AOI), verification and correction of defects in an article, and a processor operative to select between AOI, verification and correction for performing on the article.

FIELD OF THE INVENTION

This is a continuation of application Ser. No. 10/327,115 filed Dec. 24,2002. The entire disclosure of the prior application, application Ser.No. 10/327,115 is hereby incorporated by reference.

The present invention relates generally to automatic optical inspection(AOI) systems, and particularly to a system and method for automaticoptical inspection, verification and correction.

BACKGROUND OF THE INVENTION

Automatic optical inspection (AOI) systems are well known for theinspection of printed circuit boards (PCBs), flat panel displays (FPDs)and the like. AOI systems may be used to inspect various aspects andfeatures of such articles during manufacture or assembly thereof, suchas but not limited to, conductor integrity (breaks, continuity,cracking, etc.) and dimensions, insulator or substrate integrity anddimensions, hole size and placement, via size and placement, conductorpitch, line widths and lengths, artwork features, paste, componentplacement, solder joint defects and so forth.

After AOI, the article may typically be conveyed to a verificationstation for verifying whether defects discovered during inspection arereal defects. If defects are verified as being real defects, the articlemay then pass on to a correction station for correcting those defectswhich are correctable (not all defects can be corrected). In the priorart, the verification station and the correction station comprise a unitwhich is located separately from the AOI unit.

SUMMARY OF THE INVENTION

The present invention seeks to provide a system and method for automaticoptical inspection, verification and correction, which provides thepossibility of performing inspection, verification and correction at oneintegrated station. This may significantly improve throughput of AOIsystems, provide more flexibility in the manufacturing process anddiminish or eliminate bottlenecks in the manufacturing flow.

There is thus provided in accordance with an embodiment of the inventionan integrated system comprising automatic apparatus for automaticoptical inspection (AOI), verification and correction of defects in anarticle, and a controller operative to transfer an article to beinspected between an AOI location and a verification and correctionlocation. Preferably, AOI and verification and correction are performedsimultaneously on two separate articles.

In accordance with an embodiment of the invention the automaticapparatus comprises a first station comprising an AOI device and asecond station comprising a device operative to perform at least one ofverification and correction of defects in the article.

Further in accordance with an embodiment of the invention the automaticapparatus comprises a first station comprising an AOI device, a secondstation comprising a verification device operative to verify defects inthe article, and a third station comprising a correction deviceoperative to correct defects in the article.

Still further in accordance with an embodiment of the invention aconveyor is provided for conveying an article between the first andsecond (and third) stations.

Still further in accordance with an embodiment of the invention, AOIcomprises an image acquisition assembly including a plurality ofilluminators and a plurality of sensors generally extending across theentire width of an article to be inspected, such that an article to beinspected may be inspected by a single non-interrupted pass past theimage acquisition assembly in a first direction and then removed fromthe AOI by transporting the inspected article in a second directiongenerally opposite to the first direction.

There is also provided in accordance with an embodiment of the inventiona system for the automatic optical inspection (AOI) of articlescomprising an illumination and image acquisition subsystem, a firstsupport surface operative during a first time interval to support afirst article to be inspected and to transport the first article pastthe image acquisition subsystem in single uninterrupted pass to acquirean image thereof, and a second support surface operative during thefirst time interval to receive a second article to be inspected at alocation away from the image acquisition subsystem.

Further in accordance with an embodiment of the invention, the secondsurface is operative during a second time interval to support the secondarticle and to transport the second article past the image acquisitionsubsystem in single uninterrupted pass to acquire an image thereof, andthe first support surface is operative during the second time intervalto enable the first article to be removed therefrom and to receive athird article to be inspected at a location away from the imageacquisition subsystem.

Still further in accordance with an embodiment of the invention, theillumination and image acquisition subsystem is arranged along an axisextending generally perpendicularly to an axis of transport of the firstand second support surfaces.

There is also provided in accordance with an embodiment of the inventiona method for manufacturing printed circuit boards comprising providingautomatic apparatus for automatic optical inspection (AOI), verificationand correction of defects in an article, performing AOI on a firstprinted circuit board substrate, and generally simultaneously toperforming verification and correction of suspected defects, previouslyfound by AOI, on a second printed circuit board substrate.

In accordance with an embodiment of the invention the method furthercomprises performing another manufacturing step after performing atleast one of AOI, verification and correction on the article.

Further in accordance with an embodiment of the invention the methodfurther comprises diverting the article to another workstation whilecontinuing to perform at least one of AOI, verification and correctionon the article.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a simplified pictorial illustration of a system for automaticoptical inspection, verification and correction of articles, constructedand operative in accordance with an embodiment of the present invention;

FIGS. 2A-2I are simplified block diagrams illustrating operation of thesystem of FIG. 1; and

FIG. 3 is a simplified flowchart of a method for manufacturing printedcircuit boards in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which illustrates an integrated systemfor automatic optical inspection, defect verification and correction ofone or more articles 10, constructed and operative in accordance with anembodiment of the present invention. Articles 10 may comprise, withoutlimitation, electrical circuits such as printed circuit boards (PCBs),flat panel displays (FPDs), chip interconnect packaging (ICPs) and thelike.

The system may comprise, for example, automatic apparatus 12 having achassis 14 defining an inspection location 16 whereat possible defectsin article 10 may be identified, for example by means of automaticoptical inspection (AOI), and a defect verification and correctionlocation 18 whereat the possible defects in article 10 may be evaluatedas being real or false defects, and corrected, as needed.

In the embodiment seen in FIG. 1, automatic apparatus 12 comprises anAOI device 20 at inspection location 16, and a verification deviceincluding an imaging functionality, designated 22, configured to enablethe correction of at least some defects, for example by providing asufficient working distance between an article 11 and the imagingfunctionality such that a defect can be corrected manually such as byscraping away extraneous copper, at defect verification and correctionlocation 18.

AOI device 20 is operative to inspect a first article 10 to findpossible defects therein, some of which may be real defects and some ofwhich may be false defects. Verification device 22 is operative toprovide at least one of the following functionalities with respect to aninspected article 11 that has been inspected by AOI device 20: acquiringand displaying an image 23 of a possible defect in inspected article 11such that an operator may determine whether a possible defect is in facta real defect or a false defect, and enabling the operator to correct acorrectable real defect; automatically verifying whether a possibledefect found in article 11 is a correctable real defect, anon-correctable real defect or a false defect, for example by analysisof relatively high resolution image acquired by verification device 22;correcting correctable real defects in article 11; and discardingarticles 11 that have non-correctable real defects. Typical examples ofcorrectable real defects include, for example and without limitation,conductors having various protrusions some of which may result shortcircuits, copper splashes and the like. Examples of non-correctable realdefects may include, for example and without limitation, certain missingfeatures, and conductors having a severe nick, a non-localized improperwidth, breaks along conductors and the like.

In accordance with an embodiment of the invention, a correctionfunctionality associated with verification device 22 is performedmanually by an operator, or optionally automatically.

In accordance with an embodiment of the invention, verification device22 is operative such that the imaging functionality displays an image 23of a defect which is used by an operator to quickly identify falsedefects before removal of an inspected article from automatic apparatus12. Additionally, the imaging functionality may be used by an operatorwhile correcting inspected article 11 before removal from automaticapparatus 12.

In accordance with an embodiment of the invention, a suitable computerimage processor may provide an automatic false defect filteringfunctionality. Articles 11 having non-correctable real defects may bediscarded. Articles 11 having correctable real defects may be correctedbefore removal from automated apparatus 12 or passed on to a separatecorrection station along with an indication of each of the correctablereal defects in the article. The locations of false defects arediscarded such that only correctable real defects need be considered ata correction station.

In accordance with an embodiment of the present invention, verificationdevice 22 is configured such that correction may be performed atverification and correction location 18. Thus in accordance with anembodiment of the invention, verification device 22 is positioned at asufficient distance from article 11 such that an operator may accessarticle 11 to perform defect correction while simultaneously viewing animage 23 of a portion of article 11 being corrected. Optionally, anautomated functionality, designated defect corrector 24, is provided toautomatically correct at least some defects in article 11. A typicaldefect that may be corrected is excess copper such as at a copper splash26 in a printed circuit board, shown in image 23.

AOI device 20 typically comprises illumination and image acquisitionapparatus (not shown), such as but not limited to, back-lighting and/ortop-lighting apparatus, for illuminating article 10 during inspectionthereof. Article 10 may be inspected with incoherent or coherent light,for example. A preferred embodiment of illumination apparatus suitablefor use in AOI device 20 is described in copending U.S. patentapplication Ser. No. 09/719,728 entitled “Illuminator for InspectingSubstantially Flat Surfaced”, filed Dec. 13, 2000 as a national phaseapplication of PCT/IL98/00285 filed Jun. 16, 1998, the disclosure ofwhich is incorporated by reference in its entirety.

AOI device 20 may further comprise image acquisition apparatus 28, suchas but not limited to, at least one CCD (charge coupled device) array.In the embodiment seen in FIG. 1, three side-by-side image acquisitionapparatuses 28, each associated with a CCD or CMOS based imager, areprovided such that as an article 10 is transported past the imageapparatuses 28, for example in the direction of arrow 30, several imageswaths (in the example shown three, each associated with a correspondingimage acquisition apparatus 28) of article 10 are acquiredsimultaneously. In this manner, an image of substantially the full widthof article 10 may be acquired from a single uninterrupted pass ofarticle 10 by AOI device 20.

Different features on article 10 may reflect the illuminated light atdifferent intensities. For example, conductors (typically copper lines)may reflect the light at a higher intensity than the duller substrate.Thus, the features (e.g., conductors and substrate) may be recognized byan intensity of their reflected light.

In accordance with an embodiment of the invention, a computer imageprocessor 21, in operational communication with AOI device may output areport indicating suspected defects in article 10. The computer imageprocessor 21 may include, for example, hardware image processingcomponents as well as software image processing programs running on oneor more computer workstations.

Examples of an AOI device 20 that may be adapted for use in a systemoperating according to an embodiment of the present invention include,without limitation, InSpire-9000™, SK-75™, and InFinex™ series ofautomatic optical inspection systems, commercially available fromOrbotech Ltd., Yavne, Israel. These systems may be used to inspect PCBsubstrates having features and components, such as without limitation,complex fine lines or ball grid arrays (BGAs).

The acquisition of images of possible defects in article 11, such asthose found by AOI device 20, may be carried out at defect verificationand correction location 18 by various devices, such as but not limitedto, an autofocus video camera, configured for example as an autofocusvideo microscope 39 as generally described in copending U.S. patentapplication Ser. No. 09/570,972 entitled “Microscope Inspection System”,filed Jun. 15, 2000, the disclosure of which is incorporated byreference in its entirety. Video microscope 39 may be spaced from anitem on article 11, e.g., an electrical circuit, located at defectverification and correction location 18 by a distance which enablesphysical access to the electrical circuit for correction thereof.

In accordance with an embodiment of the present invention, the defectverification and/or correction functionality of defect verifier 22 isgenerally operative on an article 11 simultaneously to the inspection ofdefects in article 10 by AOI device 20 at inspection location 16. Thus,in the embodiment seen in FIG. 1, a first conveyor (not shown) isprovided for conveying an article, such as article 10, on a firstsupport surface (or table, the terms being used interchangeably) 44between the various stations. A second conveyor (not shown) may also beprovided for conveying an article, such as article 11, on a secondsupport surface (or table, the terms being used interchangeably) 46between the various stations. The first and second support conveyors incombination with the first and second support surfaces may also beconsidered as positioners operative to selectably position articles atone of the stations 16 and 18. In accordance with an embodiment of theinvention, in order to accommodate simultaneous inspecting of article 10at inspection location 16 and verification of article 11 at verificationand correction station 18, the respective conveying paths of article 10and article 11 are non-identical.

Thus, in accordance with an embodiment of the present invention, a firstsupport table 44 supporting article 10 is transported in a firstconveying plane. A second support table 46 supporting article 11 istransported in the first conveying plane at inspection station 20,however to and from inspection station 20 the second support table 46 isat least partially in a second conveying plane generally parallel tofirst conveying plane.

Reference is now made to FIGS. 2A-2I which are schematic side viewdiagrams illustrating the operation of an integrated system forinspection, verification and correction of articles in accordance withan embodiment of the present invention. Each of FIGS. 2A-2Ischematically show a chassis 114, an inspection location 116, a defectverification and correction location 118, an AOI device 120, averification device 122, a first support table 144, and a second supporttable 146. The first support table 144 and second support table 146support, respectively, articles to be inspected during inspection andsubsequent verification and correction.

In FIG. 2A, a first article to be inspected, designated 150, issupported by support table 144 and is shown being transported in thedirection of arrow 160 during automated optical inspection by AOI device120. Generally during the time interval required by AOI device toautomatically optically inspect first article 150 for defects, a secondarticle 152 is supported by second support table 146 at verificationlocation 118 while verification device 122 is operative to move, asindicated by arrows 162, to locations of suspected defects. Verificationdevice 122 is operative to acquire an image of suspected defects (notshown), which typically are displayed to an operator. It is noted thatthe performance of a verification functionality at verification location118 is optional. In some embodiments of the invention, verificationlocation 118 is used solely for loading and offloading articles from oneof the support tables 144 and 146 during the time interval used toinspect an article loaded on the other support table, without performinga verification or correction functionality thereat.

As seen in FIG. 2B, upon the completion of automated optical inspectionby AOI device, or upon verification and/or correction of all suspecteddefects in second article 152 by verifier 122, the second article 152,which has been both inspected and defects therein at least partiallyverified, has been removed from the second support table (and is notshown in FIG. 2B) and a third article 154 (seen in FIG. 2C) is placed onsecond support table 146. The first support table 144, which bears a nowautomatically optically inspected first article 150 is transportedtoward verification and correction location 118 in the direction ofarrow 162.

Next, as seen in FIG. 2C, the first support table 144, which remainsdisposed at a first level, continues to be transported in the directionof arrow 162. The second support table 146, now bearing third article154, drops down, as indicated by arrow 164, to a second level disposedbelow the level of first support table 144, and is transported towardinspection location 116 in the direction indicated by arrow 166.

As seen in FIG. 2D, once second support table 146 clears the firstsupport table 144, but generally before reaching inspection location116, it is lifted up as indicated by arrow 166 to a level required byAOI device 120 to conduct automated optical inspection.

As seen in FIGS. 2E and 2F respectively, once first support table 144reaches verification and correction location 118 and once second supporttable 146 reaches AOI location 116, the third article 154 isautomatically inspected for suspected defects with AOI device 120 whilegenerally simultaneously suspected defects on first article 150 areverified and corrected.

As seen in FIGS. 2G and 2H, once the verification and correction ofselected suspected defects on first article 150 is completed, the firstarticle 150 is removed from first support table 144 and replaced by afourth article 156 (FIG. 2H). The first support table 144 is thentransported in the direction of arrow 170 to inspection location 116.Once the automated optical inspection of third article 154 is completed,second support table 146 is dropped down to a level below first supporttable 144, as indicated by arrow 172, to clear first support table 144,and is transported away from inspection location 116 in the directionindicated by arrow 174.

Completion of the cycle is seen in FIG. 2I, wherein second support table146 is raised to a level suitable for verification and correction ofsuspected defects at verification location 118, as indicated by arrow176. Generally simultaneously to the verification and correction ofsuspected defects on third article 154, first support table 144 istransported past AOI device 120 at inspection location 118, in thedirection of arrow 170, to inspect fourth article 156 for suspecteddefects.

It is noted that in accordance with an embodiment of the invention, therelative time intervals for inspection and for verification andcorrection are mutually interdependent and may be adjusted, for exampleto accommodate inspection process constraints. Thus in accordance withan embodiment of the invention, the verification and correction may bemade time dependent on the time interval required to inspect an articlefor defects at inspection location 116. In such a configuration, onlythose suspected defects that can be verified and corrected during a timeinterval required to perform AOI are handled. If non verified suspecteddefects remain following the completion of AOI, then an article onewhich some suspected defects have been verified and other have not beenverified is passed on to an offline verification and correction stationwhere any remaining suspected defects are then verified. It isappreciated that in this mode of operation, the load at a stand aloneverification and correction station is substantially reduced, althoughit may not be entirely eliminated.

Alternatively, the integrated system may be configured to be dependenton the time interval required to verify and correct all suspecteddefects on an article. In such a mode of operation, should the timeinterval required to verify and correct defects and to place a newarticle on a support table exceed the time interval required to inspectan article for defects at inspection location 116, then the returntransport of an inspected article from inspection location 116 toverification location 120 may be delayed. Thus, this mode of operationmay be slower than a mode of operation by which operation of theintegrated system is constrained by AOI, however each article handled bythe system is inspected, verified and corrected thereby eliminating theneed for a stand-alone verification and correction station.

Reference is now made additionally to FIG. 3, which illustrates a methodfor manufacturing printed circuit boards using an integrated system forautomatic optical inspection, verification and correction of articles,in accordance with an embodiment of the present invention.

A controller 280 (FIG. 1) may be in communication with first and secondlocations 16 and 18 and tables 44 and 46, and may control the flow ofoperation of the system. Processor 280 may select between which of theoperations—AOI, verification and correction—are to provide a constraintfor completion of inspection, verification and correction of an article10, namely whether articles offloaded from the system are to bepartially or fully verified and corrected.

In accordance with an embodiment of the present invention, a portion ofan electrical circuit pattern is deposited on a substrate, such as aprinted circuit board substrate. Typically substrates are prepared in abatch, and each of the substrates in the batch is provided with the sameportion of an electrical circuit pattern.

Each substrate in a batch of substrates is provided serially to anintegrated inspection, verification and correction system such as system12 (FIG. 1), whereat a substrate is transported to an inspectionlocation and automatically optically inspected to ascertain the presenceand respective locations of anomalies suspected of being defects. Inaccordance with an embodiment of the invention, during at least part ofthe time that a first substrate is being automatically opticallyinspected, a new substrate is loaded onto the integrated system.

After completion of automatic optical inspection of a substrate, anautomatically optically inspected substrate is transferred to a defectverification and correction location located on the integrated systemwhere its suspected defects are verified as being real defects or aredetermined to be false defects, and correctable real defects arecorrected. In accordance with an embodiment of the invention,verification and correction of suspected defects on an inspectedsubstrate is performed generally simultaneously with the inspection of anew substrate.

If at least some of the suspected defects have not been either verifiedor corrected, the substrate is passed on to a stand alone verificationand correction station, for example a VRS-4 verification stationavailable from Orbotech Ltd. of Yavne, Israel, where suspected defectson the substrate are finally verified and, as needed, corrected.Substrates having uncorrectable defects are discarded. It is appreciatedthat a significantly reduced quantity of defects reach the stand aloneverification and correction station, as compared with conventionalinspection, verification and correction methods.

Once suspected defects are all verified and corrected the substrate isremoved from the integrated system. If all of the suspected defects havebeen verified and corrected, then the substrate may be combined withother substrates, and additional printed circuit board processing steps,such as application of a solder mask, may be performed to produce acompleted printed circuit board.

It will be appreciated by person skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed herein above. Rather the scope of the present invention isdefined only by the claims that follow:

1. A system comprising: a chassis, comprising: a first stationcomprising an automatic optical inspection (AOI) device which performsAOI of an electrical circuit to identify candidate defects on theelectrical circuit, and a second station comprising a verificationdevice which performs verification of candidate defects identified bythe AOI device; a first transportable support table which supports andtransports a first electrical circuit between the first station and thesecond station; a second transportable table which supports andtransports a second electrical circuit between the first station and thesecond station; and a controller which controls the first transportabletable and the second transportable table; wherein AOI is performed onthe first and second electrical circuits and verification is performedon the first and second electrical circuits without changing a relativeheight of the AOI device with respect to the chassis and withoutchanging a relative height of the verification device with respect tothe chassis.
 2. The system of claim 1, wherein the AOI device of thefirst station and the verification device of the second station areoperable to respectively perform AOI and verification simultaneously. 3.The system of claim 1, wherein the AOI device comprises an imageacquisition device comprising a charge coupled device (CCD) array. 4.The system of claim 3, further comprising a computer image processor, inoperational communication with the AOI device, which outputs a reportindicating suspected defects in an electrical circuit inspected by theAOI device.
 5. The system of claim 1, wherein the verification devicecomprises an image acquisition device which acquires an image of acandidate defect in an electrical circuit and an image display devicewhich displays the acquired image to an operator.
 6. The system of claim1, wherein the verification device comprises an automatic verificationdevice which automatically verifies, without input from an operator,whether a candidate defect identified by the AOI means is a correctablereal defect, a non-correctable real defect, or a false defect.
 7. Thesystem of claim 6, wherein the verification device is positioned asufficient distance from an electronic circuit being verified that theoperator may manually correct a defect on the electronic circuit.
 8. Thesystem of claim 1, wherein the chassis further comprises: a thirdstation comprising a correction device which corrects defects on theelectrical circuits.
 9. The system of claim 1, wherein each of the firsttransportable support table and the second transportable support talemove in a first plane when moving towards the second station and move ina second plane, different form the first plane, when moving away fromthe second station.
 10. The system of claim 9, wherein each of the firsttransportable support table and the second transportable support tablemoves from the second plane to the first plane upon reaching the firststation.
 11. A system comprising: a chassis, comprising; an automaticoptical inspection (AOI) means for performing AOI of an electricalcircuit to identify candidate defects on the electrical circuit, and averification means for performing verification of the candidate defectsidentified by the AOI means; a first transport means for supporting andtransporting an electrical circuit between the AOI means and theverification means; a second transport means for supporting andtransporting an electrical circuit between the AOI means and theverification means; and a controller means for controlling the firsttransport means and the second transport means; wherein the AOI meanscomprises means for performing AOI without changing a relative height ofthe AOI means with respect to the chassis; and wherein the verificationmeans comprises means for performing verification without changing arelative height of the verification means with respect to the chassis.12. The system of claim 11, further comprising output means, inoperational communication with the AOI means, for outputting a reportindicating a suspected defect in an electrical circuit inspected by theAOI means.
 13. The system of claim 11, wherein the verification meanscomprises: image acquisition means for acquiring an image of a candidatedefect in an electrical circuit; and display means for displaying theimage to an operator.
 14. The system of claim 11, wherein theverification means comprises automatic verification means forautomatically verifying, without input from an operator, whether acandidate defect identified by the AOI means is a correctable realdefect, a non-correctable real defect, or a false defect.
 15. The systemof claim 14, wherein the verification means further comprises: means forcorrecting correctable real defects; and means for discarding anelectrical circuit including a non-correctable real defect.
 16. Thesystem of claim 11, wherein each of the first transport means and thesecond transport means is operable to move in a first plane when movingtowards the verification means and are operable to move in a secondplane, different form the first plane, when moving away from theverification means.
 17. The system of claim 16, wherein each of thefirst transport means and the second transport means are operable tomove from the second plane to the first plane upon reaching the firstAOI means.